You can damage open/federated email without having to break the lower level layers. See winmail.dat for instance[1]. I don't know if it's still in the pipeline

You can damage open/federated email without having to break the lower level layers. See winmail.dat for instance[1]. I don't know if it's still in the pipeline but I remember that Google proposed an "AMP for email" not so long ago, with basically self-updating email contents. Open email can be severely damaged if good old SMTP is only used to tunnel proprietary formats, especially if those formats are effectively just metadata that's used to fetch the actual content of the email from 3rd parties. [1] https://en.wikipedia.org/wiki/Transport_Neutral_Encapsulation_Format https://en.wikipedia.org/wiki/Transport_Neutral_Encapsulatio...